Steel ingot making method

ABSTRACT

A method for semi-continuously casting long-length, large steel ingot by pouring molten steel into a thin walled, water cooled, long-length mold made of iron, steel or cast iron which does not thermally deform, in contact with the molten steel during pouring and withdrawing the solidifying ingot down through the mold at suitable speed without directly water cooling the solidifying ingot until a predetermined length of ingot is obtained, and then holding the ingot in the mold for a while till the ingot solidify enough to draw out from the mold on to a truck which carry away the said ingot to further processing and apparatus thereof.

United States Patent Kanokogi et al.

[54] STEEL INGOT MAKING METHOD [72] Inventors: Tatsuro Kanokogi, Osaka;Kunio Yasumoto, Hyogo, both of Japan 3,421,572 1/1969 Reihman ..l64/280X51 June 6,1972

3,455,370 7/1969 Easton et a]. ..l64/260 X 3,528,483 9/1970 Mallener 164/282 X 3,528,487 9/1970 Wognum et al l64/83 X 3,565,158 2/1971Ciochetto ..l64/83 X 3,581,806 6/1971 Neumann et a1 ..l64/83 X PrimaryExaminer-J. Spencer Overholser Assistant Examiner-John E. RoethelAttorneyRalph E. Bucknam, Jessie D. Reingold and Robert R. StrackABSTRACT A method for semi-continuously casting long-length, large steelingot by pouring molten steel into a thin walled, water cooled,long-length mold made of iron, steel or cast iron which does notthermally defonn, in contact with the molten steel during pouring andwithdrawing the solidifying ingot down through the mold at suitablespeed without directly water cooling the solidifying ingot until apredetermined length of ingot is obtained, and then holding the ingot inthe mold for a while till the ingot solidify enough to draw out from themold on to a truck which carry away the said ingot to further processingand apparatus thereof.

5 Clains, 16 Drawing figures PAIENTEBJUH 6 m2 SHEET 3 BF 4 Fig.9B

Fig.9A

DISPLACEMENT TIME I UP AND DOWN OSCILLATION CURVE |OF THE MOLD CYCLE OFCOMPRESSION AND RELAXATION OF [THE WALL OF THE MOLD Fig. l0

STEEL INGOT MAKING METHOD This application is a continuation of Ser. No.703,385, filed Feb. 6, 1968, now abandoned.

This invention relates to a method and apparatus for semicontinuouslycasting good quality steel ingot with a comparatively large crosssection and length.

Usually steel ingots have been manufactured by means of top pouringmethod in which molten steel is directly poured from ladle into a castiron mold, or by the bottom pouring method in which molten steel inintroduced from the bottom of the mold through a runner installed at thelower part of the mold. According to those conventional processes, steelingots must be drawn out from the mold after the molten steel hassolidified.

Some continuous casting methods have been also provided, in thoseprocesses molten steel are continuously cast into water cooledbottomless molds and partially solidified steel are continuously drawnout downward and then solidification of the steel is acceleated byspraying cooling water on the surface of the ingot by means of thesecondary cooling system. This cooling prevents also deformation of theingot and break out of liquid steel, thus also casting speed may beincreased.

However, these conventional casting methods have some advantages andalso some disadvantages. For example, in the top pouring method,installations are very simple and this method is widely utilized formanufacturing every size of steel ingots and various kinds of steels,but if too large are cast, a lot of molten steel will scatter due to thehead from the ladle, and scattered drops damage the steel, increasenon-metallic inclusion, especially at the initial pouring stage.Further, the above non-metallic inclusions are often entrapped in thesteel ingot, or sticked to the inner surface of the mold, causing arough surface of the steel ingot. These above mentioned disadvantagescause a lower the quality of the steel ingot, increase work load forsurface conditioning, and at the same time decrease the yields of ingot.

In the bottom pouring method, considerable amounts of expenses and workloads are required for assembling and stripping the mold, and fragmentsfrom refractory material used in a runner or guiding pipe are oftencarried into ingot with molten steel, causing defects in the ingot.Moreover the yields of ingot is lowered due to cut off of steelsolidified in the runner or pipe.

In the continuous casting method, a slab, bloom or billet can directlybe obtained. However, there is a tendency to generate various defectsinside or on the surface of cast product due to thermal and deformationstresses caused by direct water cooling or by pinch rolls under themold. Therefore, it is almost impossible to apply this continuouscastingmethod to manufacturing ingots of special steels such as l3 Cr, 18 Cr,high Mn, high C-Cr steel, etc., or rimmed steel ingot.

In recent huge steel works, various kinds of steel must be manufactured,the size of ingot becomes bigger and bigger and production speed becomesgreater, therefore the above mentioned various defects in conventionalingot casting methods become more conspicuous and it is very desirableto develop an new ingot casting technology with extensive versatility.

Object of this invention is to develop improved method and equipmentsfor semi-continuously casting large and long size ingot with excellentquality of various kinds of rimmed, semikilled and killed steel, byusing a thin walled, water cooled bottomless mold, without direct watercooling of the ingot.

Another object of this invention is to provide a method and apparatusfor preventing bulging of ingot and reducing friction between the innersurface of mold and the steel ingot being cast by forced elasticdeformation of the mold wall.

Another object of this invention is to provide a method and apparatus tohandle and truck the produced ingot ready to put into a soaking furnacefor further processing.

Above and other purposes of this invention are accomplished at first byusing a thin walled long-length water cooled mold which does notthermally deformed on pouring the molten steel. A movable bottom platein the mold receive the molten metal from a ladle at the upper part ofthe mold. The mold cools the molten steel in the mold through watercooled wall to the extent suitable for withdrawing in the mold, thebottom plate begins to descend at a desired speed holding thesolidifying steel on it, while the pouring of molten steel continues.Thus the length of the steel ingot increases gradually in the watercooled mold without any direct water cooling on the solidifying ingotsurface. When the solidified ingot becomes a predetermined length,pouring of molten steel is stopped and the solidifying ingot is held inthe water cooled mold for some length of time by stopping thewithdrawing apparatus to solidify enough suitable for withdrawing fromthe mold and loaded onto the ingot trucks and carried out to thefollowing step.

The second feature of this'invention is to use a specially designed thinwalled long length, bottomless mold made of iron, steel or cast iron.The mold has water inlet pipes and manifolds and outlet pipes andmanifolds, and is constructed of inner mold wall and outer back up wall.The cooling water channels are machined longitudially from manifold tomanifold on the outer side of the inner wall, and closed by .the backupwall. Both walls are welded together to make passages for cooling water.The upper part of the mold is rather rigidly constructed, and the lowerpart is elastically deformable. The thermal stress generated in the moldwall due to the contact with molten steel is restricted within the yieldstrength of the mold material by cooling with water, thereby anypermanent deformation of the mold being prevented.

The third feature of this invention is to provide means to reducefriction between the solidifying ingot and the mold wall and to preventbulging of the solidifying ingot caused by the ferrostatic pressure ofthe molten steel by installing a pushpull device on outside backup wallof the mold. The push-pull device periodically push inward and pulloutward the wall of the mold, that is to say, alternatively compress andrelax the wall of the mold against the solidifying ingot with relationto the up and down reciprocating motion of the mold.

The fourth feature of this invention is to provide means for reducingamount of foreign substances and non-metallic inclusion in the moltensteel and preventing entrainment of said foreign substances andinclusions inside and on the surface of the steel ingot, and alsocontrolling the direction of flow of the down-coming molten steelthereby to improve the quality of the ingot and further making easieraddition of deoxidizing agent in the molten steel.

The thin mold wall according to the present invention is constructed ofinner wall and outer backup wall, and is elastically deformable by theouter push-pull force. The inner wall made of iron, steel or cast ironcan easily be machined to have many longitudinal channels or finsthroughout the mold length, and can rigidly be welded or bolted togetherto the backup wall made of iron, steel or cast iron to make passages forcooling water. In order to extent the endurance of the mold, metalplating or plasma jetting of hard chromium or molybdenum may be appliedon the inner surface of the mold which contacts with the molten steel.The mold may be provided with any suitable means of feeding lubricant onthe inner surface of the mold. Corrosion and adhesion of dirt in thecooling water channels can also be prevented by metal plating withchromium, nickel, zinc, tin, etc. or chemical coat- This invention willbe more fully understood referring attached drawings.

FIG. 1 is an embodiment of the present invention showing a longitudinalsectional and side elevational view of a steel ingot making apparatus;

FIG. 2 is a top plan view of the steel ingot making apparatusillustrated in FIG. 1;

FIGS. 3 and 4 are longitudinal sectional views of the steel ingot makingapparatus, showing another embodiment of this invention. FIG. 3indicates the status before pouring and FIG. 4 indicates the statusafter drawing out an ingot;

FIGS. 5, 6 and 7 indicate a mold according to this invention. FIG. 5 isa top plan view of the mold, FIG. 6 is a longitudinal sectional viewtaken substantially on the vertical plane of line VI-VI of FIG. 5, andFIG. 7 is a longitudinal sectional view taken substantially on thevertical plane VIIVII of FIG.

FIG. 8 is 'a longitudinal sectional view of a truck to carry out aningot;

FIG. 9 A and B are side elevational views to explain push and pulloperation at the side of the mold;

FIG. is to explain the relation between a cycle of up and downreciprocating motion of the mold and a cycle of pushing inward andpulling outward the walls of the mold;

FIG. 1 l is a cross sectional view to explain assembling structure ofthe inner walls of the mold and the backup wall;

FIGS. l2, l3 and 14 are cross sectional views showing an example of theassembled structure of the inner wall of the mold; and

FIG. is a longitudinal sectional view which shows other embodiment whilepouring molten steel according to the present invention.

Referring to FIGS. 1 and 2, molten steel 1 is fed to the upper pouringpart of mold 5 by lifting a stopper 4 of pouring ladle 3 which istransferred above the pouring deck 2. A support 7 of a withdrawingdevice for an steel ingot is longitudinally penetrated through steelingot truck 8 from bottom and is installed in mold 5. Bottom plate 9 isconnected to the top of support 7. At first molten steel 1 is poured onthe above-mentioned bottom plate 9 in the mold 5.

When the meniscus reaches to the predetermined level in the mold, thepouring rate iscontrolled by operating stopper nozzle 4 to maintain themeniscus at the prescribed level, while support 7 is lowered togetherwith bottom plate 9 by ingot drawing out mechanism 6 such as system ofhydraulic cylinder and piston or etc. The steel ingot cooling andsolidifying in the mold which is forcibly watercooled is drawn down at asynchronous speed corresponding to the pouring speed of the moltensteel. During this step, mold 5 is subjected to continuous reciprocatingmotion by reciprocating motion device 12. The reciprocating motion ofthe mold can easily be generated by any well-known technique such aseccentric cam, crank and rod, or hydraulic cylinder. However, as shownin FIG. 10, it is desirable that the speed of downward motion of themold is made the same with the drawing out speed of the ingot andascending speed of the mold is made several .times that of the downwardmotion. It is most suitable that the distance of the reciprocatingmotion is from 5 mm to 50 mm, the cycle is from to 50 per minute and thepush-pull distance of mold wall is between 0 and 10 mm.

When the pouring of molten steel into the mold is started, push-pulldevice 13 at the central part of the mold is operated, and as shown inFIG. 9, the forced reciprocating motion to push the inner wall inwardand to pull the inner wall outward is given to wall of the mold. Asshown in FIG. 10, the operation of this push-pull device 13 issynchronized with the up and down reciprocating motion of the mold, andwhen the motion of the mold is downward, the inner wall of the mold ispushed inward and presses the surface of the steel ingot which issolidifying. When the motion of the mold is upward, the

inner wall is forcibly pulled outward, thereby friction between the moldand the ingot is released.

As shown in FIGS. 6 and 7, this push-pull device is located near thecentral part of the mold and gives alternatively push and pull action tothe inner surface of the mold, thus the walls of the mold is compressedand relaxed. A hydraulic cylinder of this device is installed on theouter backup wall of the mold, but a cam, crank or rod may be used. Thecyclic action of push and pull against the mold by the push-pull devicereduces the friction between the inner wall of the mold and ingot, andas the same time prevents bulging of the steel ingot due to the staticpressure of molten steel, thereby the drawing down of the ingot becomemore easy. However, when the cross sectional area of the mold iscomparatively small and the pouring speed is slow, the push-pull devicemay be omitted.

Thus ingot 14 is gradually drawn down within the mold 5, while beingsolidified and cooled. When the length of the ingot reaches thepredetermined length, the pouring nozzle of the ladle 3 is closed tostop the pouring, and the ingot is hold in the mold until the ingot issolidified enough to be drawn out from the mold. Support 7 of ingotwithdrawing device 6 is finally lowered to the position indicated inFIG. 8. That is, the sufficiently solidified and cooled ingot 14 iscompletely drawn out of mold 5, and set on the truck 8, the support 7 isautomatically separated from bottom plate 9 and the ingot is loaded onthe truck 8 with bottom plate 9 and the support 7 is further decend.Then, truck 8 runs on rails 17 by power to carry out the ingot to theprescribed place. Then another truck loaded with another bottom plate isset just under the mold and support 7 is raised together with new bottomplate upto predetermined level in the mold and then, the next pouringstarts again. In the example explained in FIGS. 1 and 2, truck 8 isguided on rails 17 by a chain 16, and is carried away to the position 8shown in dotted line. In order to plan more high efficiency and massproduction, the truck should be selfpropelled or be linked and pulled byan electric locomotive for successive operation. The mold must be cooledduring pouring step and for the whole period while an ingot exists inthe mold, to prevent thermal deformation of the mold. The pushpulldevice of the mold is cyclically operated during the pouring but whenthe pouring is finished, the action of the pushpull device is stopped incompression or relaxation state, thus to prevent bulging of the ingot.

FIGS. 3 and 4 show another embodiment of this invention in which theheight of the ingot making installation can be lower than that of thecurrent installation and the expense required for construction of theinstallation can be reduced. That is, the ingot truck 8 is placed justunder mold 5 and the cooled and solidified steel ingot is withdrawn byshifting mold 5 up. To this purpose, several hydraulic cylinders 15 forlifting the mold upward are installed at pouring deck 2, and, as shownin FIG. 4, the mold is lifted upward by pushing up pistons in thecylinders thereby to withdraw the solidified steel ingot, and then theingot is loaded on truck 8 and carried away. The cycle of reciprocatingmotion of the mold is synchronized with the withdrawing speed and thepush-pull motion at'the side of the mold. The cyclic action of push-pullmotion elastically deforms the wall of the mold, as shown in FIGS. 9 and10. As indicated by the dotted line in FIG. 98, when the mold is in thedown motion at the same speed as the withdrawing speed of ingot, theinner wall of the mold is inwardly compressed. When the mold is in theup motion, the wall of the mold is outwardly pulled, that is, inflatedas shown in FIG. 9A. The wall of the mold must be elasticallydeformable.

FIG. 10 illustrates the above mentioned operation. The ratio of t t t,represents time period of downward motion or compression and representstime of upward motion or relaxation, is selected between 1:1 and 10:1,according to the bulging characteristic of the steel ingot. The upperpart or pouring part of the mold is rather strongly assembled and theunder part of the mold is thin walled and lengthy and must beelastically deformable inward and outward by external force, as shown inFIG. 9. The mold is forcibly water-cooled. As shown in FIGS. 5, 6, 7 and15, the mold used in this invention is equipped with inlet pipes 21, andcooling water is led to manifold 22 from this inlet pipes 21. Then, thecooling water is collected at manifold 25 through many longitudinalchannels 24 (refer to FIGS. 11, 12, 13 and 14) installed at the innerwall of mold 23 and discharged from outlet pipes 26 and 27. The moldillustrated in the Figures is equipped with the inlet-pipe and inletmanifold at the upper part and with the outlet pipes and outletmanifolds at the bottom part. But the cooling water may be led to flowfrom the bottom toward the top of the mold.

Main characteristics of the structure of this mold for ingot making are:

1 Cooling efiiciency of the mold can be improved by selecting a properratio of cross sectional length of the mold contacting with the moltensteel (refer to FIG. 13) to total cross sectional length of the channelsof cooling water.

2 By selecting a proper thickness of the inner wall of the mold,corresponding to the thermal conductivity of the mold material (iron,steel or cast iron), the temperature increment at the inner surface ofthe mold is made less thermal deformation of the mold being kept withinallowable limit.

3. The mold can be elastically deformable because the thickness of themold is very thin.

For example, in FIGS. 1 l, 12, 13 and 14, when an iron plate with 12 mmthickness is used as an inner wall of mold 23 (42 in FIG. 13) and theingot is drawn out at speed of 300 mm/min., the maximum temperature ofthe inner surface of the mold contacting with molten steel can be keptwithin 300 C, by maintaining the flow speed of cooling water inlongitudinal cooling water channel 24 to 4 m/sec., and the crosssectional dimension of the cooling water channel to be 8.8 mm depth and4 mm width, and the pitch of the channel to be mm. According to theexcellent cooling effect, any thermal deformation caused by the thermalexpansion due to contact with the molten steel is restricted within theelastic limit or yield strength of the material of the mold, even whenthe mold is reinforced with backup wall 28 etc. Thus the wall of themold according to the present invention does not show any permanent setor permanent thermal deformation due to repeated heating for longperiod. Then the mold of the present invention can be used for longperiods of time without any thermal deformation.

FIG. 11 shows the structure of the inner wall of the mold and the backup wall. The inner wall of the mold 23 made of iron, steel or cast iron,is worked with machines to make many channels 32 and fins 31alternately. By tightly fitting back up wall 28 made of iron, steel orcast iron with inner surface of the wall, many longitudinal channels forcooling water are formed. Both walls are welded together at 34 atnecessary position through the preliminary drill hole of the back upwall, said hole in the back up wall 28 is plugged at 36 with plug 35. Orthe inner wall of the mold and the back up wall are fixed together andlongitudinal channels of cooling water 24 is constructed by preliminarydrilling small holes 37 in the back up plate and by plug-welding orbolting small holes 37 with finv part 31 of the inner surface material.The bolting method is not explained in the Figure. The cross sectionalconfiguration of the mold can be square, rectangular, poligonal orcircular, etc. However, the rectangular shape with a circular are at thecorner as shown in FIGS. 12 and 13 is commonly used. FIG. 12 explains anexample of an assembled mold in which four'sides are welded togetherwith the proper circular are R at each inner surface comer. FIG. 13illustrates an example of the angular or circular tubular mold which iscomparatively advantageous for the small cross sectional mold. An innerwall 42 of the mold is a welded angular or circular tube, and providedwith many fins 43 and channels 44 mechanically worked on the outsidesurface of the inner wall. A back up wall 45 is fixed to the inner wallto make the tubular mold. Further, FIG. 14 illustrates an example of thepartial cross section of the mold which is advantageous for making largecross sectional slab ingot mold. This mold is constructed together bywelding with four walls at 47. The circular are at comer 27 is largerthan right angle.

For prevention of abrassion and improvement of smoothness between theinner surface of the mold and the steel ingot, the inner surface of themold may be metal plated or plasma jetted by hard chromium ormolybdenum. Further, for prevention of dirt adhesion, rusting andcorrosion, and improvement of heat extraction efficiency, every innersurface of i the longitudinal channels of cooling water is metal-platedby chromium, nickel, zinc or tin, etc., or chemically treated by such asmolybdenic acid treatment and chromic acid treatment. For improvement ofsmoothness between the mold and the steel ingot, it is preferably toprovide a lubricating oil system on the mold. Vegetable oil such asrapeseed oil, various mineral oil or oils with or without properdeoxidizing agent may be used asthe lubricating oil.

As described before, one object of this invention is to provide usefulmeans for reducing the amount of foreign substances and non-metallicinclusion in the molten steel and for preventing entrainment of saidundesirable substances. One of these means is shown in FIG. 15.According to this means, molten steel 1 is at first poured from ladle 3into a ceramic crucible 72 situated at the center of the mold. Theceramic crucible has several holes 73 near bottom. As the poured moltensteel in the crucible is maintained in it for some period, dirts andnon-metallic inclusions float up to the surface of the molten steel inthe crucible, then only clean molten steel slowly flows out through theholes. The direction of flows through the hole may be changed dependingon the direction and configuration of holes 73,for example, horizontal,upward or any other desired direction.

According to this means any slag is not carried in the flow of themolten steel poured into mold, surface appearance and structure of theingot are considerably improved, and the quality of the ingot are alsogreatly improved. In this crucible, further, any type deoxidizing agentssuch as rod, strip, block or powder can easily be added into the moltensteel.

FIGS. 8 and 15 illustratethe operation for semi-continuous casting ofingot of this invention. It is desirable that bottom plate 9 can besmoothly and firmly fixed to and separated from the top of the support7. For this purpose various well-known bar connecting technics such asconnector or a conventional train coupler, etc. may beused. An actualpractice of this is explained hereunder:

When the support 7 of ingot withdrawing device 6 ascends, it isconnected to the bottom plate 9, and then further thrusts throughcentral hole of ingot truck 8. The support is, then, inserted in mold 5.As molten steel is poured into the mold, bottom plate 9 is withdrawtogether with solidified ingot thereon. The connection and disconnectionbetween the support and the bottom plate is accomplished as follows. Asshown in FIG. 8, enlarged top 53 of the support 7 fits into the concavecavity 52 of the connector 51 combined to the bottom plate. The supportis, then, held by a pair of hooks 56 which have roller 55 at one end andare pulled inward by spring 57. Roller guide plate 58 is placedslantwise, at the lower part of ingot truck 8. When a steel ingot 14 iswithdrawn downward on the truck, rollers 55 push the roller guide plate58, hook 56 is opened and, then, support 7 is automatically separatedfrom connecter 51.

What is claimed is: I

l. A method for semi-continuously casting long-length, large steelingots comprising providing a thin-walled, watercooled, long-length moldhaving elastically deformable side walls and made of iron, steel or castiron which does not thermally deform when in contact with the moltensteel during pouring, pouring molten steel into said mold, withdrawingthe solidifying ingot down through the mold at suitable speed withoutdirect cooling by water until a predetermined length of ingot isobtained, moving said mold downwardly on the downward stroke of areciprocating device and simultaneously applying a compressing, lateralmotion to the elastically deformable side walls of the mold to push saidside walls inwardly to press the surface of the solidifying ingot andprevent bulging of the latter caused by the static pressure of themolten steel, moving said mold upwardly on the upward stroke of saidreciprocating device and simultaneously applying a relaxing lateralmotion on the elastically deformable side walls of the mole to releasethe friction between the mold and the ingot, said downwardly andupwardly reciprocating motion of said mold and said compressing andrelaxing lateral motion of said mold side walls being efiectedcyclically and in synchronism, whereby the drawing down of the ingot isfacilitated by the cyclical and synchronized downwardly and upwardlyreciprocal motion relative to said compressing and relaxing lateralmotion, holding theingot in the mold for a period of time until theingot solidifies enough, drawing out the mold, and carrying away theingot to further processing.

2. A method according to claim 1 in which the thin walls of the mold arecompressed and relaxed in relation to the reciprocating down and upwardmotion of the mold to prevent bulging of the solidifying ingot and toreduce the friction between the mold and the solidifying ingot.

3. A method according to claim 1 wherein said reciprocating motion andsaid lateral push-pull motion are generally linear, such that when saidreciprocating motion is directed downwardly, said push-pull motion isdirected laterally inwardly to press the surface of the solidifyingsteel ingot, and when said reciprocating motion is directed upwardly,said push-pull motion is directed laterally outwardly to pull the innerwall of the mold laterally outwardly.

4. A method according to claim 1 further comprising circulating coolingwater through longitudinal channels in said mold, said channels havinginner surfaces coated with a metal plating.

5. A method according to claim 1 further comprising circulating coolingwater through longitudinal channels in said mold, said channels havinginner layers subjected to a molybnate and chromate chemical treatment.

1. A method for semi-continuously casting long-length, large steelingots comprising providing a thin walled, water-cooled, long-lengthmold having elastically deformable side walls and made of iron, steel orcast iron which does not thermally deform when in contact with themolten steel during pouring, pouring molten steel into said mold,withdrawing the solidifying ingot down through the mold at suitablespeed without direct cooling by water until a predetermined length ofingot is obtained, moving said mold downwardly on the downward stroke ofa reciprocating device and simultaneously applying a compressing,lateral motion to the elastically deformable side walls of the mold topush said side walls inwardly to press the surface of the solidifyingingot and prevent bulging of the latter caused by the static pressure ofthe molten steel, moving said mold upwardly on the upward stroke of saidreciprocating device and simultaneously applying a relaxing lateralmotion on the elastically deformable side walls of the mole to releasethe friction between the mold and the ingot, said downwardly andupwardly reciprocating motion of said mold and said compressing andrelaxing lateral motion of said mold side walls being effectedcyclically and in synchronism, whereby the drawing down of the ingot isfacilitated by the cyclical and synchronized downwardly and upwardlyreciprocal motion relative to said compressing and relaxing lateralmotion, holding the ingot in the mold for a period of time until theingot solidifies enough, drawing out the mold, and carrying away theingot to further processing.
 2. A method according to claim 1 in whichthe thin walls of the mold are compressed and relaxed in relation to thereciprocating down and upward motion of the mold to prevent bulging ofthe solidifying ingot and to reduce the friction between the mold andthe solidifying ingot.
 3. A method according to claim 1 wherein saidreciprocating motion and said lateral push-pull motion are generallylinear, such that when said reciprocating motion is directed downwardly,said push-pull motion is directed laterally inwardly to press thesurface of the solidifying steel ingot, and when said reciprocatingmotion is directed upwardly, said push-pull motion is directed laterallyoutwardly to pull the inner wall of the mold laterally outwardly.
 4. Amethod according to claim 1 further comprising circulating cooling waterthrough longitudinal channels in said molD, said channels having innersurfaces coated with a metal plating.
 5. A method according to claim 1further comprising circulating cooling water through longitudinalchannels in said mold, said channels having inner layers subjected to amolybnate and chromate chemical treatment.